Mr. J. Brown on the Products of the Soda Manufacture. 35 



manufactured. The ash is dissolved in boiling water until 

 the solution attains a specific gravity of 1*250 (50° Twaddell); 

 it is then run into a cistern, where it is mixed with sufficient 

 cold water to reduce the specific gravity to 1*21 (42° Twad- 

 dell). This occasions the deposition of a quantity of earthy 

 matter. A little bleach ing-powder is then added to the liquid, 

 which causes another deposition. After this has been allowed 

 to settle, the solution is carefully decanted into another pan, 

 and evaporated till it attains a specific gravity of r27 (54<° T.). 

 From this it is run into another cistern, from which it passes 

 into the crystallizing pans. The average time taken in cry- 

 stallization is eight days; but it of course varies very much 

 with the season of the year and the state of the atmosphere. 

 It is greatly assisted by placing a few bars of wood, two or 

 three inches broad, on the top of the liquor. 



The crystallized carbonate of soda thus obtained yielded on 

 analysis, — 



I. II. 



Carbonate of soda . 36*4.76 36*931 



Sulphate of soda . . 0*94.3 0*542 



Chloride of sodium . 0*424 0*314 



Water . . . . ^62*157 62*213 



100*000 100*000 



As it contains ten atoms of water rf crystallization, its for- 

 mula is NaO, CO2+ lOHO, and the per-centage composition 

 calculated from this formula is — 



Carbonate of soda , . 37*500 

 Water 62*500 



100-000 



By driving off the water from these crystals by heat, a very 

 pure carbonate of soda is obtained, which is used in the ma- 

 nufacture of glass. 



It yielded on analysis — 



Carbonate of soda 

 Sulphate of soda . . 

 Chloride of sodium . 



99*938 99*671 



D2 



